Wild Fact #93 – The Buzz-Saw Jaw – Helicoprion

Helicoprion

Early image of Helicoprion, but it is pretty close.

Today’s Wild Fact is actually on an extinct animal that lived about 270 million years ago. The Helicoprion garnered some media attention today (February 27, 2013) as a new study was published that explains the mystery of their incredible buzz-saw jaw.

Cool Things About The Helicoprion

  • Their entire lower jaw is composed of a whorl of teeth, which acts as a “buzz-saw”
  • Believe it or not the Helicoprion was long believed to be a Shark (and I thought Jaws was scary), however, the recent study has found evidence that suggests this large creature is actually part of the Ratfish family
  • Shark or not, any fish that can grow up to 7.5 metres (24.5 feet) in length and has a saw for a mouth would definitely keep me on dry land

The Buzz-Saw Ratfish

As mentioned, a new study (found here) by Leif Tapanili, Jesse Pruitt and others has finally solved the mystery surrounding the bizarre lower jaw on the Helicoprion. There have been so many drawings in the past based on old fossils, but thanks to modern technology (i.e. CT scans) they have been able to accurately reproduce the position of this jaw. For the longest time, researchers believed that they had an elongated lower jaw and the buzz-saw sat at the very end of it – they had no idea (or perhaps solid proof) that the buzz-saw WAS the lower jaw.  Interestingly, our Helicoprion researchers also discovered that this ratfish didn’t have any teeth on their upper jaw but they had the ability to keep adding teeth to continually adding teeth to the spiral.

Helicoprion

Actual tooth structure of the Helicoprion
Photo: Ray Troll, 2013

Is a buzz-saw mouth an advantage in the real world?

Apparently it wasn’t good enough to keep them around for an extra 270 million years but I don’t think we can blame their teeth for that one. While researchers are still trying to determine how this jaw worked (we can cut them some slack since they just figured out how it looks), they have discovered that as the mouth closes the teeth will rotate backwards buzz-saw like fashion. This would have been perfect for handling soft tissued prey such as squid, which was most likely was their ideal snack (or at least some creepy pre-historic squid-like animal). So to answer the questions – Yes, this dental formula probably would have been beneficial at the time, however, it was lost somewhere down the evolutionary line (thank goodness!) .

 

Source:

Tapanila L, Pruitt J, Pradel, A, Wilga CD, Ramsay JB, Schlader R, Didier DA. 2013 Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil.  Helicoprion. Biol Lett 9: 20130057.  http://dx.doi.org/10.1098/rsbl.2013.0057

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